(Not Applicable)
(Not Applicable)
The present invention relates generally to expendable decoys, and more particularly to a method for packaging infrared decoy foils within a canister which allows for controlled dispensing and dispersal of the foils. The infrared foils are typically a Special Material (SM) which, when brought into contact with air, become warm and radiate infrared energy.
As is well known in the prior art, military aircraft are typically provided with decoys which are used to draw various types of guided weapons away from the aircraft. One of the most commonly used decoy devices is a flare which is adapted to attract infrared or heat seeking guided missiles away from the deploying aircraft. In this respect, the flare is designed to present a larger thermal target than the aircraft from which it is deployed, thus attracting the weapon away from the aircraft.
Over recent years, flares have become decreasingly effective as decoy devices due to anti-aircraft weaponry having become more sophisticated and provided with enhanced capabilities to discriminate between flares and the deploying aircraft. In this respect, modern heat seeking missiles are typically provided with both a frequency discriminator which is adapted to sense the intensity of the infrared signature of the aircraft and a kinetic discriminator which is adapted to sense the speed and trajectory at which the infrared signature is traveling. When a conventional flare is deployed from the aircraft, the infrared signature produced thereby is typically more intense in the near visible frequency range than that produced by the engines of the aircraft, with the velocity and trajectory of the flare being significantly different than that of the deploying aircraft since the flare, once deployed, slows rapidly and falls straight toward the ground. The frequency discriminator of the guided missile is adapted to distinguish between the infrared signature produced by the flare and that produced by the engines of the aircraft. Additionally, the kinetic discriminator of the guided missile is adapted to distinguish between the velocity and trajectory of the aircraft and that of the flare, even if the frequency discriminator does not distinguish the infrared signatures produced thereby. As such, the combined functionality of the frequency and kinetic discriminators of the guided missile typically succeeds in causing the guided missile to disregard the deployed flare, and continue to target the aircraft.
In addition, the principal problem associated with current decoy systems is that an aircraft can only carry a limited number of them. There are not enough to allow for continuous dispensing of decoys. Therefore, the aircraft must be equipped with detectors that warn of a missile""s approach such that decoys may be dispensed. With the missile flight time very short, there is insufficient time to react in all situations. Further, such missile warning detectors are not always reliable.
In view of the above-described shortcomings of conventional flares, there exists a need in the art for a system which is adapted to create an infrared signature which is similar in magnitude or intensity to that produced by aircraft engines, appears to travel at a velocity and trajectory commensurate to that of the aircraft, and can provide continuous protection while the aircraft is over threat territory.
Prior art has developed methods of dispensing limited amounts of SM foils from aircraft. This has been done by means of stacking SM foils in a canister and ejecting them all at once using an explosive charge. The principle disadvantage of such an approach is that it provides only momentary protection since it produces one intense cloud, which does not follow the aircraft.
A preferred method is to deploy the SM foils in small packets or continuously from a canister using a drive screw or similar device. This has been accomplished successfully for relatively short stacks of SM foils by means of a piston driven by a lead screw. It has also been accomplished by packaging the SM foils into small packets, which engage a drive belt that drives them out of the canister. These methods dispense the SM foils approximately continuously such that the infrared cloud produced thereby appears to match the aircraft kinematics. They are capable of dispensing over a longer time period offering many seconds of continuous protection.
In order to provide protection for an extended period of time, it is desirable to package the SM foils into canisters which are much longer. While this can be accomplished by means of engaging individual packets of SM foils to a drive belt as described above, the method is more mechanically complex, less volume efficient and allows less flexibility in how the SM foils are dispensed than does a canister with a piston/lead screw.
Using prior art methods, problems are encountered by deploying long columns of SM foils from a piston/lead screw canister. Such canisters are typically comprised of a hollow tube with a piston at one end, and spring fingers at the other. The SM foil stack is located between the piston and spring fingers. The purpose of the spring fingers is to retain the SM foils until such time as they are forced out of the canister by the piston. The stack of SM foils has a great deal of compliance. Since none of the foils are perfectly flat, the column acts as a long spring. As the piston drives the SM foils out, the SM stack compresses against the spring fingers until they are finally let go, at which time a large slug of the SM foils is dispensed. This effect is minimal for short stacks of SM foils but prevents controlled and uniform dispensing of long stacks of SM foils.
The present invention will describe a method and related apparatus for packaging SM foils into long canisters that will allow for controlled and even dispensing therefrom.
In accordance with the present invention, there is provided a decoy pod comprising at least one elongate, tubular canister which defines a forward end and an aft end. The canister preferably has a generally square cross-sectional configuration, and defines a canister axis. Extending within the canister along the canister axis is an elongate, rotatable drive screw which includes a drive screw thread and defines a root diameter. Threadably engaged to the drive screw is a piston which is disposed adjacent the forward end of the canister. The threadable engagement between the drive screw and the piston is such that the rotation of the drive screw will facilitate the movement of the piston along the canister axis toward the aft end of the canister.
The decoy pod further comprises multiple stacks of SM decoy foils which are disposed within the canister. The decoy foils each have a generally square configuration, and are each provided with a pre-cut clearance hole within the approximate center thereof. Each stack of the decoy foils is preferably formed to have a height in the range of from about 0.5 inches to about 8.0 inches, and most preferably in the range of from about 1.0 inches to about 3.0 inches. The hole within each decoy foil is sized to allow the drive screw to easily pass therethrough.
The decoy pod of the present invention further comprises multiple separator plates which are each cooperatively engaged to the drive screw and disposed between an adjacent pair of the stacks of the decoy foils loaded into the canister. The separator plates are operative to apply a preload to respective ones of the stacks. In this respect, after each stack of the decoy foils is loaded into the interior of the canister, a separator plate is installed on top of the just loaded stack. The separator plates each have approximately the same form as the decoy foils, i.e., a thin, generally square configuration. Additionally, each of the separator plates is formed to include at least one hole in the approximate center thereof which is sized and configured to allow each of the separator plates to be pushed over and along the drive screw without the need to rotate the drive screw. More particularly, the hole of each separator plate is preferably sized to have a diameter which is slightly smaller than the root diameter of the drive screw. Additionally, each separator plate is preferably formed to include a pair of elongate primary slots which extend in generally parallel relation to each other along opposed sides of the hole. In addition to the primary slots, a pair of secondary slots are formed in each separator plate which extend radially from the hole to respective ones of the primary slots. The primary and secondary slots of each separator plate are sized and configured to allow the hole to expand around the drive screw when pushed thereover, and to cause the separator plate to engage the drive screw in a manner resisting the opposing pressure produced by the preloaded decoy foils.
In an alternative embodiment, each of the separator plates may be formed to include multiple slots which extend radially from the hole thereof, and are sized and configured to allow the hole to expand around the drive screw when pushed thereover, and to cause the separator plate to engage the drive screw in a manner resisting the opposing pressure produced by the preloaded decoy foils. In a further alternative embodiment, the hole within each of the separator plates may be internally threaded so as to be threadably engageable to the drive screw threads of the drive screw by producing relative rotation between the drive screw and the separator plate. As will be recognized, the primary and secondary slots and radial slots described above allow the hole of the corresponding separator plate to expand when forced over the drive screw, and more particularly the drive screw threads thereof.
The decoy pod of the present invention further comprises an end closure which is cooperatively engaged (i.e., threadably connected) to the drive screw and operative to apply a preload to the last loaded stack of decoy foils, i.e., the stack disposed closest to the aft end of the canister. The end closure preferably includes a sealing member which extends about the peripheral edge thereof and is disposed in sealed engagement to the interior surface of the canister. Additionally, at least two and preferably four spring fingers separated by intervals of approximately 90 degrees are preferably cooperatively engaged to the canister at the aft end thereof. As indicated above, in the present decoy pod, each separator plate is installed over the drive screw and preloaded onto the stack of decoy foils beneath it. The preload applied to each stack by its corresponding separator plate is preferably greater than or equal to the force required to push the decoy foils through the spring fingers located at the open aft end of the canister. In this respect, the stacks of decoy foils are pre-compressed by the separator plates and act as a rigid, incompressible column, thus providing for the controlled and even dispensation of the decoy foils from within the canister. As a result, the decoy foils of the present invention may be packaged into canisters which are much longer than was possible using the prior art.
As indicated above, the rotation of the drive screw in the present decoy pod is operative to facilitate the movement of the piston along the drive screw toward the aft end of the canister. Since the stacks of the decoy foils and the separator plates are disposed between the piston and the aft end of the canister (and more particularly the end closure), the movement of the piston toward the aft end results in the dispensation of the decoy foils therefrom. As will be recognized, the initiation of the rotation of the drive screw causes the end closure to be initially jettisoned from the decoy pod, with the decoy foils thereafter being dispensed therefrom stack by stack. As indicated above, the preferred sizing of the stacks and preloading thereof by the separator plates causes the decoy foils to be evenly and uniformly dispensed through the spring fingers located at the aft or exit end of the canister. Advantageously, the preferred size of the canister makes it capable of holding a sufficient quantity of the decoy foils to offer approximately five (5) minutes of continuous protection. A plurality of these canisters (typically six and preferably seven) can be installed within the interior of the decoy pod or upon another location of the aircraft. The decoy foils can then be expended or dispensed sequentially from the canisters, thus offering thirty (30) minutes or more of continuous protection from infrared guided missiles.
Further in accordance with the present invention, there is provided a method of packaging a multiplicity of infrared decoyed foils into a canister having an aft end and a drive screw extending therein. The present method allows for the controlled dispensing and dispersal of the decoyed foils from the canister, and comprises the initial step of segregating the decoy foils into multiple stacks. The stacks are than advanced one at a time into the interior of the canister, with a preload then being applied to each of the stacks other than for the stack disposed closest to the aft end of the canister through the use of multiple separator plates which are cooperatively engaged to the drive screw such that each of the separator plates is disposed between an adjacent pair of the stacks. The present method further comprises the step of applying a preload to the stack disposed closest to the aft end of the canister through the use of an end closure cooperatively engaged to the drive screw. The cooperative engagement of the separator plates to the drive screw is preferably accomplished by pushing the separator plates over the drive screw without rotating the same. Alternatively, the separator plates may be threadably engaged to the drive screw by producing relative rotation therebetween.
Thus, the present invention provides a packaging method for infrared decoy foils within the canister which allows for the controlled dispensing and dispersal of the decoy foils therefrom. As indicated above, the decoy pod of the present invention comprises a canister and a drive screw which engages the internal piston and end closure, and extends to an external engagement fitting. The rotation of the drive screw releases the end closure and causes the piston to drive the foils out from within the interior of the canister, and hence from within the decoy pod. The even dispensing of the decoy foils is assured by the multiple separator plates which are located at intervals within the decoy foils, and engage the drive screw in a manner facilitating the application of the preload to the decoy foils.